A hinge structure normally includes two hinge members which are rotatably secured together by a pin or the like. Automatically operated doors, such as those commonly used in shopping centers, schools or the like are continually operated and are substantially heavier and larger than those used in most homes. As will be understood, continual use of the door submits the hinge structure to extensive wear. Notwithstanding their continual use and the substantial load placed thereon, a hinge structure is expected to perform error-free and with minimum maintenance.
Increases in height and/or weight of the door or the like carried by the hinge member, adds to the frictional sliding contact between the hinge members and thereby increases the wear on the hinge structure. As may be appreciated, and despite the wear on such hinge structures, the hinge members are not normally permitted to longitudinally move relative to each other during their operation.
My U.S. Pat. No. 3,092,870, dated June 11, 1963, discloses a pinless hinge structure offering increased performance and durability. Such a hinge structure includes two longitudinally extending hinge members which are rotatably joined along adjacent longitudinal edges by intermeshing gear segments forming part of the hinge members. A clamp member maintains the gear segments in mesh relative to each other while permitting smooth and uniform movement of the hinge members through a full arc of travel of the hinge. The clamp member has a generally C-shaped cross section whose inwardly turned ends are formed with longitudinally extending rod-like portions. Each rod-like portion on the clamp member fits within a longitudinal channel formed in the gear segment and defines a fixed axis of rotation for each hinge member.
When the hinge structure is closed, it is desirable for the clamp member to be brought close to the hinge members to enhance security The hinge members of my patented design, however, rotate about fixed axes. Therefore, the clamp member is normally arranged at a fixed distance from the hinge members when the hinge structure is closed. The ability to arrange the clamp member proximate to the hinge members further enhances aesthetic features of the hinge structure.
The design and performance of the hinge structure disclosed in the above-identified patent was further enhanced through the provision of a longitudinal thrust bearing assembly which was the subject of my U.S. Pat. No. 3,402,422, dated Sep. 24, 1968. My patented longitudinal thrust bearing assembly inhibits longitudinal movement of one hinge member with respect to the other hinge member.
Preferably, several thrust bearing assemblies are longitudinally spaced along the length of the door to distribute their load-bearing capability. Because the hinge members rotate about fixed axes, the gear segments have limited or local contact with the bearing assembly. Despite their improved performance, and because of their localized contact about fixed axes of rotation which is limited to the cross-sectional area of the gear segment (which is reduced by the longitudinal channel formed therein to accommodate the rod-like portion of the clamp member), relative sliding engagement between the hinge members and the thrust bearing do, on occasion, result in wear thus requiring replacement of the thrust bearing assembly.
Replacement of any or all of the thrust bearing assemblies normally requires complete disassembly of the hinge structure from the associated door. As will be appreciated, repairs on a door leading to a commonly frequented building such as a school, hospital, or the like, interrupts or limits accessibility to such a building. Even if only for a short time period, such interruptions to building access are undesirable and, therefore, should be maintained to a minimum if not eliminated. As will be appreciated, any change in the hinge structure design which will facilitate an increase in performance of either the hinge structure or the bearing assembly would be beneficial.